The present invention refers to a process for the sealing of smallest crevices, chinks and/or openings in walls of housings against penetration of fluids, the use of the process, housings of electrical or electronic devices having crevices, capillaries, chinks, openings and the same which have to be sealed against penetration of fluids, but not against penetration of gases as well as a battery compartment of a hearing aid device.
In particular with medical devices which are worn on the human body, there exists the danger that under the influence of humidity, perspiration, etc. certain parts and components of the device may corrode and not operate properly anymore. Especially penetration of fluids and perspiration into hearing aid devices may cause corrosion e.g. of the battery and in certain cases may cause disturbances of the electronic as well as of the electro-acoustical transducer. Correspondingly, various processes are described to make hearing aid devices more resistant against penetration of fluids.
In the DE 19502994A1 a watertight hearing aid device is described in which the characteristic of water tightness is achieved by complicated constructive measures such as gaskets and membranes. The DE 3834316C1 describes a completely watertight hearing aid device but does not show, compared to the patent application mentioned before, in detail how the water tightness is achieved but lays more stress on describing in detail the design of watertight operating elements. Again, in the JP 11069498, the U.S. Pat. No. 5,249,234A and the U.S. Pat. No. 6,510,230B2 various approaches are described to protect HdO-devices by using a protection envelope against the penetration of humidity. This protection envelope contains, according to the design, also materials to absorb perspiration or humidity.
In the US 2002/0181725A1 a condenser-microphone with a hydrophobic membrane is described to prevent the sticking together with the backplate and also various methods how the hydrophobic characteristic can be achieved.
The US 2002/100605A1 describes a hydrophobic coating for housings of electrical devices, in particular in relation to over-voltage conductors. Again, in further documents hydrophobic coatings of substrates are described, such as polymers, wood, concrete, etc., for which the above mentioned problem is no topic.
In particular medical devices which are worn on the human body, such as pulse frequency measuring devices, invasive detecting sensors for blood characteristics, such as oximetry-sensors, heart frequency measuring devices, hearing aid devices and the same are usually complicated devices which consist out of a plurality of individual mechanical or electronic components which are produced by using various processes and are finally assembled. Due to the mechanical tolerances of the injection moulding, plastic parts which in most cases are used for housings, battery compartment covers, switches and the same, microscopic capillary crevices can always accrue between the individual components also at the assembled status of the devices.
As most of these medical devices, such as e.g. hearing aid devices, are operated with zinc-air-batteries, it is not possible to close the device hermetically, as the battery needs a constant supply of oxygen to maintain the operation voltage. Of course, this requirement is also possible for other electronic or electrical components which need certain aeration. The consequence is that a complete impermeability, as it is described partly in the state of the art, is not suitable. Also complicated mechanical constructions with the use of gaskets and porous membranes, as they are known out of the state of the art, are not appropriate and make medical devices usually bigger and more expensive.
It is very difficult to envisage the influence of capillary crevices by designing a hearing aid device or generally of a smallest medical device. But as mechanical constructions for preventing penetration of liquids at existing device designs are not any more possible without any difficulties, it is a subject of the present invention to make medical devices, as in particular smallest devices and hearing aid devices, permeable without the need of changing, the design. It is also essential that at the complete sealing against penetration of humidity still a certain permeability of gas is present within the capillary crevices.
With the development of hearing aid devices and the same, the trend is going more and more into the direction of modular components which can be combined for constructions of different devices. To reduce working hours and costs and the improvement of reproducibility, also for so called in-the-ear hearing aid devices, an improved modularity is aspired. The inherent problems with modular systems are the mentioned capillary crevices which may accrue at the assembling of the individual modules to a device. Through these capillaries the penetration of fluids into the hearing aid device is accelerated.
Finally, the possibility fails to produce the hearing aid device out of a water repellent hydrophobic material which could reduce the wettability and therefore the penetration of fluids through capillary crevices fails, as it would not change anything about the fact that such materials like Teflon can neither be processed by ordinary processes, nor the mechanical and aesthetic criteria may be achieved.